(1) Field of the Invention
The present invention relates to a packet relaying apparatus with a payload reconstruction function, and more particularly to a configuration to enhance the packet processing efficiency.
(2) Description of the Related Art
In connection with the scheduled discontinuation of terrestrial analog broadcasting, the possibility of using so-called IP broadcasting, namely digital broadcast transmission conforming to the Internet Protocol (IP), is studied as a solution to the problem of a blanket area or defective area in receiving terrestrial digital broadcasts. It is proposed to configure the network for carrying out IP broadcasting with Fiber-Distributed Data Interfaces (FDDIs) from the transmitting apparatus to home inlets and with the Ethernet from home inlets to receiving apparatuses.
In IP broadcasting, a plurality of TS (Transport Stream) packets are forwarded a an IP packet from by adding a header to a set of TS packets. In usual packet forwarding in conformity with IP, the total size of packet is limited by a maximum transmission unit (MTU) defined for each physical layer of the communication path. For instance, the MTU for the Ethernet is 1,500 bytes and that for the FDDI is 4,352 bytes.
When an IP packet having a size greater than the MTU of the communication path is transmitted, a relaying apparatus located at the entrance of the communication path will divide that IP packet into a plurality of IP packets (IP fragmentation). Japanese Unexamined Patent Publication NO. H10-190734 (patent document 1) discloses a technique for dividing an IP packet into a plurality of packets having a suitable size by a packet relaying apparatus when the IP packet is transmitted from a communication path with a larger MTU to another communication path with a smaller MTU.